Releasable permanent magnet holding device



M. BAERMANN, JR

May -1 0, 1 938.

' RELBASABLE PERMANENT MAGNET HOLDING DEVICE Filed July 22, 1935 [III]BY 4. iflM ATTORNEY Patented May 10, 1938 RELEASABLE PATENT OFFICEPERMANENT MAGNET HOLD- ING DEVICE Max Baermann, Jr., Cologne, GermanyApplication July 22,

In Germany Thainvention relates to a releasable permanent magnet holdingdevice particularly for electric lamps which will adhere in any positionto objects made of ferro magnetic materials.

It is known to provide electromagnets in the foot of an electric lampbut the use of such electromagnets has in practice many disadvantages.Direct current is necessary for their excitation, and that, unless D. C.mains are available, must be taken from a battery. When there are D. C.mains they commonly have so high a voltage that a magnet lamp supplieddirectly from them is dangerous to use.

Where there is an A. 0. supply this danger may be avoided bytransforming down the voltage; but then a rectifier is necessary forsupplying the electromagnet. So that in both cases complex apparatusliable to go out of order is necessary for the operation of a magnetlamp.

A further disadvantage of the known arrangement is that if the currentfails, or falls oil on account of faulty contact, defect in therectifier, or failure of the supply, the lamp no longer adheres, andunless the lamp is otherwise sufllciently supported it falls.

These disadvantages are avoided in the present invention by the use ofpermanent magnets of so high a coercive force .as to ensure adherence ofthe device to a support. A suitable material for such permanent magnetsis an alloy having a coercive force of more than 240 and preferably morethan 300 Oerst'edt.

To give the support and holder maximum utility a further feature of theinvention contemplates the combination of magnets and pole shoes in theshape of a horseshoe magnet so that two similar flat poles, preferablyof prismatic cross section, stand opposite one another, each terminatingin two similar projections bounded on their ends by a plurality ofmutually inclined planes. This form of pole shoe has in the middle ofits contact surface a notch broadening outward while the outer edges arebevelled oil. Such a shape of pole face in combination with thehorseshoe form is of great importance as regards the adherent powersince two separate magnet poles will almost always be able to seatthemselves simultaneously upon an object of whatever form it may be.Other forms of magnet, for instance, the iron clad magnet in which acentral pole is surrounded by an annular pole, do not always enable bothpoles to contact with an object, moreparticularly if the latter has acurved airface. But the horseshoe form with projections bounded byslanting surfaces will suit almost 1935, Serial No. 32,878

July 23, 1934 any profile sufllciently to ensure the But a support orholder fitted with such strong I magnets could only be lifted from anobject by the use of great force. A further feature of the 5 inventiontherefore contemplates the provision of a short circuiting device forthe magnetic flux which facilitates the removal of the holder from anobject to which it has been adherent. The magnetic short circuit ispreferably in the immediate neighbourhood of the pole pieces forexperiments have shown that with such strong magnets a short circuit isnot always effective enough if applied only to the rear part of themagnet pole.

In accordance with the invention the two pole shoes are of U form withlimbs of different length and are arranged on the two sides of themagnet with their shorter limbs applied to the magnet and the longerlimbs forming the pole pieces, and the short-circuiting plate isarranged at the curve of the pole shoes. In this construction of themagnet limb a short-circuiting plate may be arranged on the rear side ofthe pole pieces without impairing the short circuiting action. Theproduction of this form of holder is simple, cheap and easy.

An electric lamp may be attached to the holder'in any suitable fashionas, for example, by means of a wing nut. But the holder may be employednot only for supporting electric lamps but also as a support or hangerfor any objects whatever. Where considerable strength is needed theinvention provides a flat plate in which several separate permanentmagnets are arranged one beside the other with their unlike polesopposite. To remove such a plate from an object to which it-is adherent,or to remove objects from the plate, the poles of the separate magnetsmust be short-circuited.

Such short-circuiting may be effected by movement to and fro of ashort-circuiting armature at the rear of each magnet, preferably so thatthe several armatures move in succession and not simultaneously tolessen the power needed. For this purpose the armatures are preferablyconnected with cams upon a common shaft so ar-. ranged that when aparticular position is reached all the armatures are freed and appliedto the poles of the magnets. Such an arrangement is especially ofadvantage for magnets carried in a plate andhaving U-shaped pole shoessince the short-circuiting armatures may without detriment to theshort-circuiting efl'ect be applied to the rear faces of the pole ends.

ill

Instead of effecting the short-circuiting by means of separate armaturesit may be eflected by a leaf spring which in the short-circuitingposition contacts with all poles and is pressed away from thempl ya camor the like separating from them one after the other owing to itselasticity.

The accompanying drawings show examples of construction of theinvention. 1 I

Figure 1 is a vertical longitudinal section through a holder with U-shaped pole shoes.

Figure 2 is a detail end view showing the form or the pole pieces ofFigure 1.

Figure 3 is a vertical section through e-plate with inset magnets andwith armatures actuated by a cam shaft.

Figure l is a view" at right angles to 3 section on the line E f-IV ofFigure u e 5 is a vertical. section through a oset magne Winch theseparate maghe shcrt-circuited by a leaf spring.

"""gure 6 is a plan of the plate.

the construction of holder shown in Figure 1 two iii-shaped pole pieces[3 with limbs of unequal length are secured by their shorter limbs M tothe bar magnet l5 by means of a bolt l6, while the longer limbs l1 formthe pole pieces. Each pole shoe l3 terminates in two projections l lbounded by inclined surfaces so that between the projections there is anotch broadening outward, while the outer edges of the projections arebevelled. This form of projection enables the device to contactsufficiently not only with concave and'jcpnvex surfaces but also withprofiles of almost any form. The short-circuiting plate I9 is applied tothe flattened bends l8 oi the pole shoes l3. When the holder is requiredto adhere to an object of magnetic material this plate is turned bymeansoi the bolt 28 attached to itand so lifted from the pole shoes bythe action of a pin it upon the curved surface oi the guide bush 22. Athumb piece 23 serves for turning the bolt to. The guide bush 22, thebolt 2e and a casing 2t surrounding the whole device are made oinon-magnetic material such as brass. On the pole piece side the deviceis protected irorn ingress of iron particles and dirt by a plate 25 oinon-magnetic material such as brass.

When large surface is required to which ar .tioles are to adhere or whengreatstrength is necessary as, for instance, in chucks, a number oiadherent devices 2? may be mounted in a plate it or non-emagneticmaterial such as brass, their pole shoesloeing oi the form shown inFlg== are l. The several armatures 28 are actuated by cams 30 upon a.common shaft 29, the cams being of such form that on turning the shaftthe armatures are lifted in succession from the magnets and in an endposition are all applied to the magnets. Figures 3 and 4 illustratingthis mechanism are of a diagrammatic character, but those skilledin theart will readily understand how to shape the cams with the necessarydwell to cause the armatures to be applied in succession, each armaturethen remaining-in engagement however until all are engaged.Alternatively, as shown in Figure 5, short-circuiting may be eflooted bya spring 3i which in the short-circuiting position contacts with all themagnets. Here again the figure is diagrammatic and in practice thespring 6 might need to be made thicker at any rate in the parts formingthe actual armatures, to c y the pressed dot i '1; cam causes to eparatefrom the several in succession.

F. claim:

1. releasable permanent magnet hold ng device comprising a permanentmagnet, iii-shaped pole shoes having limbs of unequal length, theshorter limbs being applied to the ends of said magnet, ashort-circuiting armature, and means for bridging said armature acrossthe bends oi the pole shoes and removing it therefrom.

2. A releasable permanent magnet holding device comprising anon-magnetic plate, a plurality of permanent magnets mounted in saidplate, an armature for each magnet movable with respect to said plateinto and out of short circuiting position relatively to its magnet, ashaft, and cam means thereon co-operating with the said armatures uponrotation of the shaft to remove them successively from their magnets.

3. A releasable permanent magnet holding device comprising anon-magnetic plate, a plurality of permanent magnets mounted in saidplate with their poles in one a spring secured to said plate and lyingalong the line of poles, and means for pressing ,the end of said springaway from said poles so that said spring separates from the severalpoles in succession.

l. A releasable permanent magnet holding device comprising a permanentmagnet, U shaped pole shoes having limbs of unequal length, the shorterlimbs being applied to the ends of said magnet, a'siiort circuitingarmature, and means including a rotatable shaft and a cam for bridgingsaid armature across the bend of the pole shoes and removing ittherefrom;

MAZQ-BAERMABW, Jim.

